The invention relates to developing apparatus for a photocopying machine or the like of the type with a reservoir for toner, the underside of which reservoir is bounded by a shell made out of non-magnetic material, which shell surrounds a magnetic roller and serves to transfer the toner to an adjacent electrostatically charged outer surface of a drum for facilitating photocopying. A doctor blade is provided to adjust the coating thickness of the toner material at the shell, which doctor blade extends in the axial direction of the shell and is radially adjustable with respect to the shell.
An exact adjustment of the radial distance of the doctor blade from the outer surface of the shell is of importance in establishing a uniformly thick layer or coating of toner at the shell over the entire length of the shell. With known developing apparatus, this adjustment of the distance or spacing of the doctor blade to the shell causes difficulties. In these known arrangements, the doctor blade is fastened to the housing of the toner reservoir by means of screws extending through the doctor blade. After loosening of the screws, the doctor blade can be adjusted by means of the play in its bores, whereafter the screws are again tightened. This form of adjustment is especially time consuming and awkward for servicing work. Even more importantly, this arrangement is inexact and unreliable because the danger exists that during the tightening of the screws, the doctor blade will move relative to the shell and the selected adjustment is again lost.
The invention is directed toward solving the problems in building a developing apparatus of the above-mentioned kind that facilitates a simple and exact adjustment of the spacing of the doctor blade to the shell. These problems are thereby solved according to the invention in that the doctor blade is arranged in a radially extending slide guide at the circumference of the shell and is held in the radial direction with respect to the shell by means of adjustable adjusting elements arranged in the region of the respective two opposite ends of the shell.
With this arrangement, according to the invention, it is possible in a simpler manner to obtain an exact adjustment of the doctor blade so that a truly uniform thickness toner layer can be obtained. Because the adjustment possibilities are actually very exact, it is also possible to adjust the spacing by smaller amounts than previously was normal.
In an advantageous preferred embodiment of the invention, it is provided that a wall of the reservoir chamber extending radially with respect to the shell and several leaf springs together form a U-shaped slide guide facing the shell. The doctor blade is guided in this slide guide without play. In the region of the reservoir opposite the shell radially extending treaded bores are disposed in a protrusion at the reservoir between the radially extending reservoir wall and the leaf springs. Adjusting screws are arranged in these bores which abut against the upper surface (radially outermost surface) of the doctor blade opposite the shell. In order to facilitate a play-free adjustment of the doctor blade, the upper surface of the doctor blade is resiliently held against the adjusting screws by means of springs.
Further objects, features, and advantages of the present invention will be more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, one embodiment in accordance with the present invention.